How potassium came to be the dominant biological cation: of metabolism, chemiosmosis, and cation selectivity since the beginnings of life

In the cytoplasm of practically all living cells, potassium is the major cation while sodium dominates in the media (seawater, extracellular fluids). Both prokaryotes and eukaryotes have elaborate mechanisms and spend significant energy to maintain this asymmetric K+/Na+ distribution. This essay proposes an original line of evidence to explain how bacteria selected potassium at the very beginning of the evolutionary process and why it remains essential for eukaryotes.

Automated summary

Potassium is the major cation in the cytoplasm of almost all living cells, while sodium dominates in the extracellular fluids. Both prokaryotes and eukaryotes require elaborate mechanisms and significant energy to maintain the asymmetric distribution of K+ and Na+. This essay presents original evidence explaining how bacteria chose potassium at the beginning of evolution and why it remains essential for eukaryotes.